REACTIVE ION ETCHING OF SILICON STENCIL MASKS IN THE PRESENCE OF AN AXIAL MAGNETIC-FIELD

A reactive ion etching (RIE) system with a magnetic field, mainly para llel to the dark space electric field on the etch electrode, is descri bed. This axial-field REE system has been used with a molecular bromin e (Br-2) plasma to fabricate Si stencil masks for ion beam lithography . Silicon dioxide (SiO2) films were used as masking layers, and the et ching process was optimized for smallest silicon wall angle at a const ant Si/SiO2 selectivity of 50. The optimized process was used to fabri cate 0.75-1.0-mu m-thick Si masks with sub-50 nm resolution. Over a th ickness of 0.75 mu m, change in linewidth was found to be less than 10 nm, corresponding to a wall angle of less than 0.2 degrees or 3 mrad. (C) 1995 American Vacuum Society.